4-methoxyphenylacetic acid

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of 4-methoxyphenylacetic acid for effects in the environment:

 

The chemical 4-methoxyphenylacetic acid (CAS no. 104-01-8) is used for as an intermediate in chemical synthesis, as a laboratory chemical and as an Agrochemical herbicide/pesticide. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for 4-methoxyphenylacetic acid. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.

 

 

Persistence assessment

The tested substance does not fulfils the P criterion within Annex XIII based on the assessment that here follows:

 

Biotic degradation

Estimation Programs Interface Suite (EPI suite, 2017) was run to predict the biodegradation potential of the test compound 4-Methoxyphenylacetic acid (CAS no. 104 -01 -8) in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI LInear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that 4-Methoxyphenylacetic acid is expected to be readily biodegradable.

 

Biodegradation study was conducted for 20 days for evaluating the percentage biodegradability of test substance 4-Methoxyphenylacetic acid. Bacteria was used as an inoculum. The test was performed under aerobic conditions at a temperature of 25°C.The chemicals were introduced into the BOD bottles as sole carbon sources at a concentration of 2 mg of carbon per bottle. The compounds were added in acetone solutions, and the acetone was evaporated prior to the addition of 02-saturated water. Each bottle received 5 mg of Hudson Collamer silt loam as a source of the microbial inoculum. The bottles were filled with the air-saturated salts solution and closed with glass stoppers. Bottles containing O2 saturated water inoculated with soil (as a source of microbial inoculum) but no carbon source were also included in the study to account for the O2 depletion resulting from microbial oxidation of organic matter and ammonium. Test compound was also tested in combination with glucose (both at a conc. of 2 mg of carbon per bottle) to test whether the possible lack of biodegradation was a result of toxicity of the test chemical. Dissolved O2 in the bottles was measured at regular intervals using a Yellow Spring Instrument Co. oxygen analyzer, Model 53.The instrument was calibrated with the salts solution, the O2 content of which was determined by the Alsterberg modification of the Winkler method. At regular intervals, the dissolvedO2in the samples was measured after calibrating the instrument with a BOD bottle containing inoculated 02-saturated water supplemented with 0.1% KCN. The solutions in bottles showingO2depletion were used to obtain microorganisms capable of utilizing the substrate. Based on appreciable degradation of test chemical after only a few days, 4 -Methoxyphenylacetic acid is considered to be biodegradable in nature.

 

Various experimental studies on read across substances (CAS: 619-86-3 and 100-09-4) also indicate the substances to be readily biodegradable.

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 72.5%). In soil, 4-methoxyphenylacetic acid was expected to have rapid mobility based upon a Log KOCof 1.15. Thehalf-life in soil (30 days estimated by EPI suite) indicates that the chemical is not persistent in soil and the exposure risk to soil dwelling animals is low.

 

If released in to the environment, 27.4 % of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2017). However, the half-life (15 days estimated by EPI suite) indicates that the exposure risk to aquatic animals is moderate to low.

 

Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% when estimated by EPI Suite version 4.1).

 

Hence it has been concluded that 4-methoxyphenylacetic acid is not persistent in nature  

 

 

Bioaccumulation assessment

The tested substance does not fulfil the B criterion within Annex XIII based on the assessment that here follows:

 

The estimated BCF value (EPI Suite, 2016) was determined to 3.162 L/kg wet wt and the octanol water partition coefficient of the test chemical is determined as 1.29 which is less than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.

 

Toxicity assessment

The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:

 

Mammals

The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).

 

Aquatic organisms

All of the available short-term eco-toxicity estimation for fish, invertebrates and algae for the substance indicates the LC50/EC50 value to be above 100 mg/L. These value suggest that the substance is likely to be non-hazardous to Aquatic organisms at environmentally relevant concentrations and can be considered to be not classified as per the CLP regulation.

 

There are no available long-term toxicity evaluations for 4-methoxyphenylacetic acid. By speculation, long-term NOEC for aquatic organisms were not expected for 4-methoxyphenylacetic acid at concentration below 0.01 mg/L based on the data mentioned above.

 

The chemical was therefore not considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.

 

Conclusion

Based on critical, independent and collective evaluation of information summarized herein, the tested compound does not fulfil the P, B and T criterion and has therefore not been classified as a PBT compound within Annex XIII.